Although beneficial in agriculture, pesticides can become environmental toxicants when they interact with non-target species. Many of these toxicants have detrimental effects on human health. In order to predict the potential health effects of exposure it is critical to know what traits are affected, as well as understand the genetic basis for how those effects are produced. Understanding how genetic variation contributes to susceptibility will ultimately allow the identification of individuals who are most likely to be adversely affected by exposure to these environmental toxicants. Unfortunately, we are limited by the lack of a model experimental genetic system to study the effects of environmental toxicants at the level of whole organism traits and even more limited at the level of the population. The long-term aim of my research program is to use the model genetic system, Drosophila melanogaster, to study the genetic basis underlying susceptibility to environmental toxicants in natural populations. The overall goal of this proposal is to study the effects of an herbicide on male reproductive performance in D. melanogaster, investigate genome-wide changes in gene expression after exposure, and begin to explore how natural genetic variation affects reproductive susceptibility to this herbicide. Our work will enable future projects to dissect the genetic mechanisms of susceptibility, elucidate the pathways and systems that are important, and predict how exposure will affect reproductive capability. Ultimately, we hope to be able to identify individuals at risk for being adversely affected by exposure to environmental toxicants. PUBLIC HEALTH RELEVANCE: Environmental toxicants, such as pesticides, are serious threats to human health but the genetic basis underlying their effects can be difficult to study in humans. The proposed research will establish the model genetic system, Drosophila melanogaster, as a model toxicology system to study the effects of environmental pollutants on reproductive performance and start to identify novel genes that are involved in responding to these environmental stressors.